The present invention relates generally to an angular position sensing system and, more particularly, to a variable reluctance angular position sensing system for measuring the angular displacement of a rotating shaft.
Variable reluctance sensing systems used to measure the angular displacement of a rotating shaft are known in the art. In many typical applications, variable reluctance sensing systems are used in conjunction with internal combustion engines, such as automobile or motorcycle engines, to measure the rotational speed of various components within the engine. For example, many variable reluctance sensing systems are used to measure the angular displacement of the engine camshaft or the engine crankshaft while the engine is operating. Sensed angular displacement data can be provided to an electronic engine control system to control engine performance events, such as, engine ignition events, fuel injection events, as well as other similar engine functions or performance events.
FIG. 1 illustrates a typical variable reluctance sensing system 10 used to measure the angular displacement of a rotating shaft 12, such as, an engine crankshaft or camshaft. As shown in FIG. 1, the sensing system 10 typically includes a sensor 16 having a magnet 20 that is disposed through a side wall of the engine housing 18. The sensor 16 can be used to detect the position and speed of a rotating toothed or slotted wheel 14 (e.g., a spur gear) that is rigidly secured or attached to the rotating shaft 12. The sensor 16 and the slotted wheel 14 create a magnetic flux path (e.g., a magnetic circuit) between the two poles of the magnet 20. In particular, the magnet 20 establishes a magnetic field through the slotted wheel 14 and the housing 18 as shown by the dotted field lines in FIG. 1. As the slotted wheel 14 rotates, the sensor 16 detects and/or measures any changes in the magnetic flux through the magnetic circuit. Furthermore, as mentioned above, the sensor 16 can be electrically coupled to an electronic controller that can be used to control engine performance events (e.g., fuel injection, engine ignition, etc.) to improve engine performance.
There are several shortcomings with most existing variable reluctance systems. For example, while most existing variable reluctance sensing systems are accurate and reliable, they cannot be readily implemented on existing engines not equipped to accommodate these systems. To accommodate most existing variable reluctance sensing systems, significant modifications to the engine (including the engine housing 18 and/or the rotating shaft 12) are typically required. Making such modifications to an engine not previously designed to accommodate a variable reluctance sensing system would be time consuming and costly. Furthermore, because at least a portion of the magnetic field travels outside of the engine housing 18, the strength of the magnetic flux through the magnetic circuit may be degraded due to interference.
Improvements in angular position systems used to measure the angular displacement of a rotating shaft are, therefore, sought.
The present disclosure relates generally to a sensing system. More particularly, the present disclosure relates to a variable reluctance sensing system for measuring the angular displacement of a rotating shaft. In one aspect of the disclosure, the sensing system comprises a rotor and a sensor assembly disposed within the rotor. The rotor is constructed and arranged to be securably mounted to the shaft such that the rotor rotates in concert with the shaft. Furthermore, the rotor defines a plurality of teeth extending radially inwardly towards a center of the shaft. The sensor assembly comprises a sensor housing and a magnet arrangement disposed within the housing. The magnet arrangement defines a magnetic flux path between the sensor assembly and the rotor. As a result, the magnet arrangement and the rotor cooperate to define a magnetic circuit. Changes in magnetic flux through the magnetic circuit can be measured to determine the angular displacement of the rotating shaft.
Further to this aspect, the sensing system comprises an electrical conductor in electromagnetic communication with the magnet arrangement. The electrical conductor is adapted for providing an input signal to an electrical control system. The input corresponds to the angular displacement of the shaft. The electrical conductor can comprise a helical coil in electromagnetic communication with the magnet arrangement.
Still further in this aspect, the magnetic arrangement can include a permanent magnet and at least one magnetic extension. The magnetic extension is in electromagnetic communication with and extends away from a pole of the magnet to a position proximate to a periphery of the rotor. Alternatively, the magnetic arrangement can include a first and second magnetic extension. The first magnetic extension can be arranged such that it is in electromagnetic communication with and extends away from a first pole of the magnet to a first position proximate to a periphery of the rotor. Conversely, the second magnetic extension can be arranged such that it is in electromagnetic communication with and extends away from a second pole of the magnet to a second position proximate to the periphery of the rotor opposite the first position.
Still further in this aspect, the first magnetic extension can be in electromagnetic communication with the magnet via a first support member extending laterally from the first pole of the magnet. Similarly, the second magnetic extension can be in electromagnetic communication with the magnet via a second support member extending laterally from the second pole of the magnet.
The sensing system can be configured to detect a first extended valley defined in the plurality of teeth. The period between the detection of the first extended valley corresponds to time taken to complete a single revolution of the shaft. Alternatively, the sensing system can be further configured to detect a second extended valley defined in the plurality of teeth opposite the first extended valley. The period between the detection of the first extended valley and the second extended valley corresponds to time taken to complete a half revolution of the shaft.
In another aspect, the sensing system comprises a rotor and a sensor assembly disposed within the rotor. In this aspect, the rotor can be secured to the shaft such that the rotor rotates in concert with the shaft. Furthermore, the rotor defines a plurality of teeth extending radially inwardly towards a center of the shaft. The sensor assembly can comprise a sensor housing and a magnet arrangement disposed within the sensor housing. The magnet arrangement defines a magnetic flux path between the sensor assembly and the rotor. The magnet arrangement can comprise a permanent magnet and at least one magnetic extension in electromagnetic communication with and extending from a pole of the magnet to a position proximate to a periphery of the rotor. The sensing system also can comprise an electrical conductor in electromagnetic communication with the magnet arrangement. The electrical conductor can provide an input signal to an electrical control system corresponding to the angular displacement of the shaft.
Further to this aspect, the electrical conductor can comprise a helical coil in electromagnetic communication with the magnet arrangement. The magnetic arrangement can further include a first magnetic extension in electromagnetic communication with and extending from a first pole of the magnet to a first position proximate to a periphery of the rotor. The magnetic arrangement can further include a second magnetic extension in electromagnetic communication with and extending from a second pole of the magnet to a second position proximate to the periphery of the rotor opposite the first position.
Still further in this aspect, the first magnetic extension can be in electromagnetic communication with the magnet via a first support member extending laterally from the first pole of the magnet. Similarly, the second magnetic extension can be in electromagnetic communication with the magnet via a second support member extending laterally from the second pole of the magnet.
Still further in this aspect, the sensor assembly can be configured to detect a first extended valley defined in the plurality of teeth. The period between the detection of the first extended valley corresponds to time taken to complete a single revolution of the shaft. Similarly, the sensor assembly can be further configured to detect a second extended valley defined in the plurality of teeth opposite the first extended valley. The period between the detection of the first extended valley and the second extended valley corresponds to time taken to complete a half revolution of the shaft.
In still another aspect, the present disclosure provides a method of installing a variable reluctance sensing system for measuring the angular displacement of a rotatable shaft disposed through an existing housing. The method can comprise securing a rotor coaxially to the rotatable shaft; the rotor being adapted to rotate in concert with the shaft; situating the rotor at a desired orientation; aligning a sensor assembly with the rotor secured to the shaft; securing the sensor assembly to the housing such that the sensor assembly is disposed within and fixed in relation to the rotor.
Further in this aspect, aligning the sensor assembly with the rotor can include aligning one or more alignment holes defined through the rotor and the sensor assembly; inserting one or more corresponding alignment pins through the alignment holes defined through the rotor and the sensor assembly to maintain the rotor fixed with respect to the sensor assembly while the sensing system is being installed; and removing the one or more corresponding alignment pins once the sensor assembly is secured to the housing. Once the sensor assembly is secured within the housing, the method can further comprise securing a cover to the housing to enclose the sensor assembly within a cavity defined by the housing.